Many ailments and conditions of the human body require the administration of medication into the lungs of the patient. Typically, medication is provided by way of a metered dose inhalation (MDI) apparatus, comprising a pressurized container of the medication with appropriate valving to dispense a fixed amount of medication upon activation of the valve unit. The medication is inhaled to deliver the dispensed dose to the lungs.
While the amount of medication released per MDI cycle is accurately metered, the amount of medication actually reaching the lungs is far from consistent. To direct the medication to the lungs, the user must create an inspiratory flow of air, and must further time the flow to capture and engage the flow of medication, normally in the form of a mist, as it is released by the MDI. In addition, the high velocity of the emitted spray often results in a large portion of the drug being deposited in the mouth and oropharyngeal area, causing an unpleasant aftertaste, drug loss, and on occasion candidiasis.
To assist the user, a variety of devices have been developed to channel the MDI output. These devices, called "spacers", typically create a residence volume to accept the atomized spray until a breath is taken. Often, however, these devices introduce additional problems and complications, including awkwardness of use and the creation of complicated mechanisms which can defeat the inherent simplicity of the MDI system. The devices also often fail to gain user acceptance, as they are not small enough to provide the chronic respiratory disease patient with the ability to use the unit inconspicuously.